Scholarship & Research
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Item Using genetic and genomic techniques to uncover cryptic diversity for improving aquatic invasive plant management(Montana State University - Bozeman, College of Agriculture, 2021) Chorak, Gregory Michael Thomas; Chairperson, Graduate Committee: Ryan Thum; This is a manuscript style paper that includes co-authored chapters.Genetic diversity can be important at many levels of invasive species management. And, for different questions, it matters at which level we measure diversity to understand its relevance. Some invaders may look similar to other species, so identifying the species to be managed may be difficult without genetic tools. Once the species has been identified, understanding the diversity in that species may be important to identify management units, invasive traits, and the possibility of spread. Finally, understanding how the alleles an individual possesses determine the traits expressed can give managers the tools to control for unwanted traits of an invasive species. In this body of work, I uncover diversity at the species/taxon level, the genotype/clone level, and finally at the gene level in invasive aquatic weed species. At the taxon level, I found that one invasion of aquatic weeds in the northeastern US was actually two or more separate invasions and taxa. At the genotype level, I found that the same genotype responds the same to a common herbicide management regardless of where it is found, and that different genotypes have varying responses to a common herbicide treatment. And, at the gene level, I found that different genotypes with different growth rates have different gene expression in the control and transcriptional response to a common herbicide treatment. At each of these levels, managers have questions and concerns about management decisions. Understanding that there were two unique taxa in what was considered one invasion informed managers that there may be variance in management relevant traits between the two. In the genotype level study, we learned that determining which clones are present in a lake slated for herbicide management may inform which herbicides to use. And, at the gene level, we are starting to understand the molecular process of management relevant phenotypes so that one day managers can screen for molecular markers that will reveal herbicide response of individuals slated for management.Item Management of Kochia (Bassia scoparia) in a time of herbicide resistance(Montana State University - Bozeman, College of Agriculture, 2020) Lim, Charlemagne Ajoc; Chairperson, Graduate Committee: Alan T. Dyer; Alan Dyer and Prashant Jha were co-authors of the article, 'Kochia (Bassia scoparia) growth and fecundity under different crops and weed densities' submitted to the journal 'Weed science journal' which is contained within this dissertation.; Alan Dyer and Prashant Jha were co-authors of the article, 'Survival and reproductive fitness of glyphosate-resistant kochia (Bassia scoparia) in the presence of glyphosate' submitted to the journal 'Weed technology journal' which is contained within this dissertation.; Alan Dyer and Prashant Jha were co-authors of the article, 'Survival, growth and fecundity of Dicamba-resistant kochia (Bassia scoparia) in the absence and presence of Dicamba' submitted to the journal 'Weed technology journal' which is contained within this dissertation.Kochia [Bassia scoparia (L.) A. J. Scott] is one of the most troublesome weeds in the US Great Plains. This is exacerbated by the development of herbicide-resistant kochia populations which necessitates more ecologically driven approaches for its control. This research examined the competitive effects of four crops (sugar beet, soybean, barley and corn) in combination with kochia densities (3, 13, 24, 47, 94 and 188 plants m-2) on kochia development and kochia seed production. Corn had greatest effect in reducing kochia biomass and seed production. Barley had greatest effect in delaying kochia flowering which happened after barley senesced at 113 days after kochia emergence. Soybean and sugar beet had the least effect in reducing kochia biomass and seed production, respectively, relative to fallow. This research also reports the fitness of glyphosate-resistant kochia and dicamba-resistant kochia in the presence and absence of glyphosate and dicamba selection, respectively, under field conditions. Glyphosate-resistant kochia showed limited fitness cost (less seed weight and seed radicle length relative to the susceptible) in the absence of glyphosate selection and reduced reproductive fitness (seed production) in the presence of increasing glyphosate selection. In the absence of dicamba selection, dicamba-resistant kochia showed a fitness cost (reduced growth and seed production relative to the susceptible) associated with dicamba resistance with greater fitness cost observed with increased level of resistance. Dicamba-resistant kochia also showed reduced reproductive fitness (seed production) in the presence of increasing dicamba selection. Overall, this research provides information on the growth and reproductive fitness of glyphosate-resistant kochia and dicamba-resistant kochia in the presence and absence of glyphosate and dicamba selection, respectively. Furthermore, this research provides insights on the competitive abilities of different but financially viable rotational crops for kochia management in Montana.